Question 277566
First factor {{{x^2-18x+81}}}


*[invoke change_this_name4450 1,-18,81, "x"]



So {{{A=3.14(x^2-18x+81)}}} then becomes {{{A=3.14(x-9)^2}}} which is of the form {{{A=pi*r^2}}} where 'r' is the radius. So the radius is {{{r=x-9}}}. Since "radius greater than 9", this means that {{{r>9}}} and {{{x-9>9}}}. Solve for 'x' to get {{{x>18}}}